This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present techniques. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present techniques. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
Liquid impact loads are found in innumerable circumstances. Some of the most common impact systems are associated with liquid motion in confined spaces, which can include loading from fuel in fuel tanks (e.g. automobile, airline, or marine vessels), bulk liquid carriers (e.g. LNG tanker ships, oil tanker ships, milk tanker trucks, etc.); manufacturing processes (e.g. etching, engraving, painting, ink jet printing); vehicle dynamics where impact while coming in contact with fluid (e.g. airplane water landings, high speed planing craft), combustion processes, to name a few. In liquid carrying applications, it is generally desired to reduce the liquid impact load of the liquid on the container holding the liquid. This is most often accomplished by attenuation using a variety of specially designed internal shapes and protrusions. See, e.g. U.S. Pat. No. 7,469,651. The fuel in a fuel tank may be handled differently due to issues specific to combustible fuels and expansion of gasses at high altitudes. See, e.g. U.S. Pat. No. 6,698,692. The manufacturing cases have heretofore been viewed as non-analogous, but such a system includes a liquid impact on a solid object and the present disclosure may be applied to such systems to improve efficiency of jet dispersal, control diffusion or improve the momentum transfer.
Depending on fill level, LNG sloshing can be categorized into high-fill (fill level larger than 80%) and partial-fill conditions (fill level between 10%-80%). Partial-fill typically occurs during offshore cargo-transfer while high-fill typically occurs during LNG transportation. Offshore cargo-transfer may be preferable to onshore transfer for several site-specific reasons associated with onshore terminals (e.g. limited land, water depth, population congestion, etc.). However, the sloshing loads under partially filled conditions can be significant even under small sea states. As a result, it may be necessary to restrict offshore cargo-transfer to a small operation envelope (e.g. sea state with significant wave height 1.5˜2.0 meters) to avoid conditions where the resulting sloshing impact pressure may damage the ship structure. This complicates cargo-transfer operations. Emergency suspension of discharge operations and evacuation from the terminal may be necessary if the sea state rises while loading or unloading. In other cases, LNG carriers may have to idly wait for cargo-transfer windows to open due to the small operation envelope. Both of these cases have a negative impact on offshore cargo-transfer operation economics and safety. For high-fill applications, there is still some risk of sloshing (e.g. liquid impact) damage in high seas or after a number of round trips.
Conventional approaches to the problem of sloshing generally rely on numerical methods. However, numerical method based approaches are generally deficient in that such methods cannot be scaled to size and are generally limited to providing qualitative (but not quantitative) information. For example, conventional approaches may predict the average force exerted on a structure in contact with a liquid but cannot adequately predict the actual force on a particular point or area of interest. Similarly, many prior art solutions to the sloshing problem have either not addressed partial fill sloshing issues, or require significant redesign of the container tanks (e.g., LNG tanks) themselves.
What is needed are methods and systems to accurately predict and control liquid impact loads on surfaces that are applicable over a wide range of applications. What is further needed is a solution to the sloshing problem that addresses the issues of partially filled liquid containers without requiring changes in the container's geometry, internals, or overall design.